I think we should just close this as WONTFIX. The idea that SVN should
transliterate filenames based on whatever the local filesystem supports
is frankly horrible. One can always rename the file in the repository
(although access to older versions would still not be possible).

Alternatively, the solution might be to allow "permanently missing"
files in the working copy (that is, files that appear in .svn/entries,
but are marked as "don't create"). Their status would have to be checked
at every update to see if the name had changed, and would add even more
spaghetti to our WC code.